1. Field of the Invention
The present invention relates to a compressor and more particularly to an absorptive silencer of a compressor.
2. Description of the Prior Art
Generally, a compressor is used in a refrigeration cycle and the compressor comprises, as illustrated in FIG. 1, a stator 20, a rotor 21 and an eccentric unit 16a formed at an end of a crank shaft 16.
The eccentric unit 16a of the crank shaft 16 is attached to a connecting rod 11 for changing a rotary motion of the crank shaft 16 to a reciprocating motion and the connecting rod 11 is coupled to a piston 12 by a piston pin 13. The piston 12 repeats absorption and compression of refrigerant in a cylinder block 70.
The cylinder block 70 is coupled to a cylinder head unit 90 by a coupling bolt (not shown), and an absorptive silencer 100 is provided at a refrigerant inlet side of the unit go to reduce noise generated when the refrigerant is sucked from outside by reciprocation of the piston 12.
The material of the absorptive silencer 100 is polybutylene terephthalate (PBT), which consists of PBT resin, glass fiber (30%), coupling agent (0.1%) and paraffin wax (0.3%), where the coupling agent is silicone oil.
The glass fiber is used in the composition of PBT for fire-resistance, and the coupling agent is used for achieving good mixture between PBT resin and glass fiber, and the paraffin wax is an additive for producing good extrusion.
Sometimes, hydrofluoro carbon-12 (HFC-12, C.sub.2 F.sub.4 H.sub.2 -12) is used as a refrigerant, which is a good material for use in a compressor, and a mineral oil-based refrigeration oil is used sometimes in that refrigerant.
However, as a way to protect the earth environment, hydrofluoro carbon-134a (HFC-134a, C.sub.2 F.sub.4 H.sub.2 -134a) is currently used as a refrigerant, and esther-based refrigeration oil is used. When refrigerant and oil thus described are used in a reciprocating compressor having an absorptive silencer extruded from PBT, the PBT resin and the esther-based refrigeration oil react to generate oligomer which blocks the refrigerating cycle, i.e., a phenomenon of blocking a capillary tube occurs.
Furthermore, the capillary tube is clogged by the mixture of paraffin wax and esther-based refrigeration oil, which reduces the refrigeration efficiency or provides a cause of refrigerator glitch.